Cathode-ray tube electrode



Sept. 11, 1951 E. POHLE ET AL 2,567,893

' CATHODE RAY TUBE ELECTRODE Filed May 6, 1949 2 Sheets-Sheet 1 -High lalfage E l Electrode I I5 l5 H Y m.- /f// F' Fig.2

INVENTOR.

ER/G POHLEA 8y 'ALFRED Y. BENTLEY Arrow/5g Sept. 11, 1951 Pol-[LE T AL2,567,893

CATHODE RAY TUBE ELECTRODE INKENTORS ER/c POHLE By ALFRED K BENTLEY wwwPatented Sept. 11, 1951 CATHODE-RAY TUBE ELECTRODE.

Eric Pohle and Alfred Y. Bentley, Passaic, N. J., assignors to Allen B.Du Mont Laboratories, Inc., Passaic, N. J., a corporation of DelawareApplication May 6, 1949, Serial No. 91,714

4 Claims.

This invention relates to cathode ray tubes and particularly to theelectrode structures therein.

In the utilization of higher voltages on the electrodes of cathode raytubes, difliculties arise from corona discharges from any sharp edges onthese electrodes adjacent the space across which high voltage exists.This often causes spurious emission of electrons from these points,which, accelerated by the higher potentials of the succeedingelectrodes, are caused to impinge at random n the fluorescent screen.This causes an overall illumination of the screen which reduces contrastand is therefore objectionable.

Some of these spuriously emitted electrons impinge on the succeedingelectrodes themselves, thus increasing the beam current by effectivelyadding a leakage current which is not necessarily constant and whicheffectively may cause fluctuations in the light output of the screen.

In addition, sharp edges very often produce distorted fields and resultin defocussing of the beam.

- Accordingly, an object of our invention is to provide an improvedelectrode and mounting for same.

Another object is to provide an electrode having rounded edges and whichcovers or shields all sharp edges or corners of the supporting member.

still another object is to provide an electrode so shaped that highfrequency currents are readily produced in the center of the electrodeinsuring proper de-gassing during processing without appreciable heatingof the fastening members thereby reducing thermal expansion andeliminating possibilities of metal evaporation onto insulating members.

Using this invention, these objects may be achieved easily andeconomically.

The invention may be understood from the description in connection withthe drawing, in which:

Figure l is a side view of a cathode ray tube partly in section andhaving one embodiment of the invention, and the relation of cooperatingparts;

Figure 2 is a view through 2-2 of Figure 1;

Figure 3 is a side view, partly in section, of an alternative embodimentof the invention; and

Figure 4 is a plan view of the elements of Figure 3.

A preferred form of the invention is shown in Figure 1. A cathode raytube ID has as one electrode therein a flanged aperture cup I I havingan aperture I2 in the center thereof. For the purpose of mounting thecup II on supporting rods an opening I! is formed such as by piercing inthe elongated portions or tabs Hand 20 extending from the flanged edge2|. The edges around the opening I! are bent inwardly. Also, the edgesof the flange 2| and the outer edges of the elongated portions I9 and 20are bent back to present a rounded surface in the direction of thelongitudinal axis of the cup.

Split eyelets I 3 are secured to th aperture cup II on the underside ofthe elongated portions l9 and 20 and coaxial with the opening [1. As maybe seen in Figure 1, the bent edges around the opening I! extendinwardly into the upper open end of the eyelet l3 and the outer edge ofthe elongated portion I 9 extends beyond and around the outer edge ofthe upper end of the eyelet l3. The eyelet l3 may be secured by anysuitable means as by spot welding, for instance.

Supporting rods l5, which may be metallic or ceramic are insertedthrough the eyelet l3. The ears M of the eyelets are then squeezedtogether and welded, thus securely fastening the cup II to the rod l5.

In many gun designs, the second grid must be rather shallow to conservespace, and by means of the split eyelets extending below, sufficientbearing surface is made available for gripping the side rods to make arigid structure. This is particularly important when the side Or supportrods 15 are of ceramic material, for during the subsequent processing ofthe tube, the metallic parts are heated by induced high frequencycurrents, and the unequal coefiicients of thermal expansion may tend toloosen the metal parts from the ceramic unless a suflicient bearingsurface is provided.

It will be noted that with all edges of the electrode bent back, roundedsurfaces are presented. The edges of the adjacent or consecutivefollowing electrodes in the tube may also be bent back so as to preventa rounded edge. In this way, each electrode presents a rounded surfaceto the adjacent consecutive following electrodes. This, of course,reduces any discharge from sharp edged surfaces.

Further, it will be noted that with the structure provided the elongatedportions of the aperture cup I I form a complete shield over the spliteyelet used for mounting the cup. Furthermore, no sharp edges areprovided around the mounting or supporting means.

Referring to Figure 3, which shows another embodiment of the invention,the flanged aperture cup II is connected to support rods I5 by means ofhalf collars or straps I6 which grip the outside of the cup portion I I,and which also grip the support rods l5. As in the embodiment shown inFigure 1, the half collars extend around the rod l and are clampedthereto and spot welded to provide a rigid structure.

While this invention has been specifically described as applied to asecond grid electrode of a cathode ray tube, where, because of the shal-10W construction, the problem has been particularly acute, it is by nomeans limited to this particular use. This method of construction may beapplied to other electrodes operated at high voltages.

What is claimed is:

1. An electrode for a cathode ray tube which comprises a metallic discwith a saucer shaped depression therein and an aperture in the centerthereof, the edges of said disc being bent back to presentlongitudinally a rounded end, a mounting tab having a hole therein, andlocated on the side of said disc with the edges of said tab bent back toextend in the same direction as the edges of said disc, a support rodextending through said hole, a split eyelet secured to said tab saideyelet surrounding said support rod and being clamped thereto, the edgesaround said hole being depressed to form a seat for said split eyeletand a rounded surface on the other s de thereof, the rounded edgeportions of said disc and said mounting tab covering and forming ashield over said split eyelet, there being a continuous smooth surfacefrom said disc extending beyond and around said rod.

2. An electrode for a cathode ray tube which comprises a metallic discwith a saucer shaped depression therein, and an aperture in the centerthereof, the edges of said disc being bent back forming a rounded end, amounting tab extending from the edge of said disc and having an openingfor a support rod, the inner and outer edges of said tab being bent backin the same direction as the edges of said disc, a support rod clampingmeans securing said disc to said support rod passing through said hole,the rounded edge portions of said disc and said tab covering and forminga, complete shield over said clamping means, said tab being secured tosaid disc on the side thereof toward which said edges are bent, therebeing a continuous smooth surface from said disc extending outwardlybeyond and around said opening.

3. In a cathode ray tube an electrode comprising a shallow circular dishportion having an aperture therein, a radial rim on said dish portionhaving two holes therein at diametrically opposite locations, all of theradially outermost edges of said rim being turned down in the samedirection as the bottom of said dish, the edges of said holes being alsoturned down in the same direction, a pair of split eyelets attached tosaid rim adjacent said holes, each of said eyelets comprising acylindrical body portion having a longitudinal slot therein, tabsextending substantially radially from said body portion adjacent saidslot, and a flared end portion, said eyelets being welded to saidelectrode with the flared end portions thereof being adjacent thedown-turned rims of said holes, said eyelets being covered and shieldedby said rim, there being a continuous smooth surface extending from saiddish portion beyond and around said holes.

4. In a cathode ray tube, an electrode comprising a shallow circulardish portion having an' aperture therein, the edges of said dish portionbeing turned back to form smooth, rounded edges, an opening in thesurfaces of said dish portion, the edges around said opening beingturned back to form smooth, rounded edges, an annular clamp secured tosaid dish portion on the under side thereof and adjacent said opening,the surface of said dish portion covering and shielding said annularclamp, there being a continuous smooth surface from said dish portionextending beyond and around said opening.

ERIC POHLE. ALFRED Y. BENTLEY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,299,047 Winans Oct. 13, 19422,303,166 Laico Nov 24, 1942 2,383,571 Spangenberg Aug. 28, 19452,429,824 Koch et al Oct. 28, 1947 2,432,037 OLarte et a1 Dec. '2, 19472,436,264 OLarte et a1 Feb. 17, 1948 2,461,743 Krahl Feb. 15, 19492,468,136 Taylor Apr. 26, 1949 FOREIGN PATENTS Number Country Date14,860 Australia Sept. 12, 1935 of 1933

